With increasing development of internet and communication technologies, the living styles of people are deeply changed. As the internet and communication technologies become more powerful, more powerful processors or large-scale integrated circuits are required to process data. However, since the processing capability for the processors or large-scale integrated circuits increase, the power consumption also increases. Therefore, it is important to increase the converting efficiency of the power converters of the processors or large-scale integrated circuits.
Conventionally, the method of powering the server system or the communication system provides a relatively lower bus voltage (e.g., 12V). Moreover, by a power converter, the low bus voltage is converted into regulated voltages for powering the processors or large-scale integrated circuits. As the power consumption of the processors or large-scale integrated circuits increase, the current withstood by the low voltage bus bar gradually increases. The power consumption of the bus bar is proportional to the square of the current on the bus bar. Without decreasing the wiring impedance of the bus bar, the power consumption of the bus bar increases with the square of the current. Consequently, the conventional method of powering the server system or the communication system wastes energy and generates a great deal of heat. The generation of heat decreases stability and reliability of the server system or the communication system.
For solving the above drawbacks, some approaches are disclosed. In accordance with an approach, a relatively higher voltage (e.g., 48V or more) is provided to the bus bar to centralize the efficacy of powering the server system or the communication system. In case that the load power is unchanged, the current for the bus bar applied by 48V bus voltage is one fourth of the current for the bus bar applied by 12V bus voltage, and thereby the power consumption corresponding to 48V bus voltage is one sixteenth of the power consumption corresponding to 12V bus voltage. Consequently, the use of the high bus voltage to power the server system or the communication system can largely reduce the power loss of the bus bar.
Generally, the power supply voltage of the processor or the large-scale integrated circuit is low. Consequently, if the voltage difference between the power supply voltage of the processor or the large-scale integrated circuit and the received bus voltage of the power converter is higher, the converting efficiency is lower. In case that the bus voltage is high, the converting efficiency of the two-stage power converter is superior to the converting efficiency of the single-stage power converter.
FIG. 1 is a schematic circuit diagram illustrating a conventional power converter. As shown in FIG. 1, the power converter 1 is for example a two-stage power converter and comprises a first stage converter 10 and a second stage converter 11. The first stage converter 10 receives an input voltage Vin(e.g., a bus voltage) with a higher magnitude (e.g., 48V) and converts the input voltage Vin into an intermediate voltage Vmid. The second stage converter 11 receives the intermediate voltage Vmid and converts the intermediate voltage Vmid into an output voltage Vout. The output voltage Vout is used for powering a load 12 such as a processor or a large-scale integrated circuit.
In the conventional method of controlling the second stage converter 11 of the power converter 1, the output voltage Vout is only used as the parameter to be controlled. However, since the output voltage Vout is the only parameter to be controlled, the converting efficiency of the second stage converter 11 is not surely optimized in all possible load conditions (e.g., a light load condition or a heavy load condition) while achieving the output feature. The problem of the first stage converter 10 is similar to the problem of the second stage converter 11. That is, the converting efficiency of the first stage converter 10 is not surely optimized in all possible load conditions.
Therefore, there is a need of providing a power converter and a control method in order to overcome the above drawbacks.